new home insulation ????s and others

[froggy_loves_heddley]

Hi, I plan on having a new home built this year. I am going to do some of the work myself and have a few questions. It is going to be a small, 1400 SF, home and I hope to make it VERY energy efficient.

I am going to use spray foam insulation in the walls and ceiling. I've read of the unvented, semiconditioned method of doing an attic, but I am leaning towards foaming the attic floor and adding blown in on top. The roof will be galvanised metal over foil faced decking. I feel it is wasteful to allow the heat in my home to go up through an uninsulated ceiling to semicondition the attic during the winter. The galvanised metal or radiant barrier decking should keep a lot of heat from entering the attic in the summers. Any reason why I should consider the other method?

I'm going to apply 1 inch of foam in the walls and batts over that. I know I dont need a vapor barrier, but what about a radiant barrier on the under the drywall on the walls and ceiling? I feel that would make it very cozy in the winter. Would another layer of radiant barrier under the outer siding help even more?

Any ideas, suggestions or other help is appreciated.

[hallerb]

closed cell foam is over R6 per inch, thats way better than any batt material.

true its upfront cost is more but it will reward you with a lifetime on energy savings. plus foam seals all the little airleaks making for a more energy efficent and quieter home, as air leaks conduct noise.

Go with a foot of foam for R 72 walls and R100 cielings. since your building theres a HVAC program that can show furnace BTUs needed, heating cost per year, as the insulation is upgraded.

[ransley]

There are several foam types one is about R 5 one is about R 7.2" One inch is not much. SIPs houses are 6" of foam for walls and some use

12" for the attic-roof. Depending on where you live, your Zone, consider 2x6 construction and all foam. If you dont vent the attic you could have big condensation problems. A tight house will need an air exchange system. 1" foam and 2.5 of batts is only maybe R 14, that is not optimal

[Edwin Pawlowski]

Sounds like you are on the right track. I'd also consider using ICF's or SIPS for a tight strong house.

is one of many ICF's available. Good tornado protection too if you are in the areas that has them.

[ransley]

ng. =EF=BF=BDI

1400sq ft R 72 walls, R 100 ceiling might need 30,- 40,000 btu or with a good design with the sun.

[froggy_loves_heddley]

king. =EF=BF=BDI

I'm in Texas near Dallas, so I think the R72 walls and R100 ceiling are overkill. My main question was foam the roof versus foam the attic floor. And the radiant barrier on the underside of the ceiling and under the drywall on the walls.